1. Field of the Disclosure
The present disclosure provides methods and apparatus for navigating a drill string through a reservoir layer of an earth formation.
2. Description of the Related Art
Drilling apparatuses used in oil exploration make it possible to drill a borehole horizontally through an earth formation. Generally, horizontal drilling occurs in a formation layer that is of particular interest, such as a petroleum-bearing layer or reservoir. When drilling, it is desirable to maintain the drilling within the reservoir without straying into an adjacent formation layer. Fortunately, the adjacent formations typically have electromagnetic properties that differ from the properties of the reservoir and which may therefore be used for navigational purposes. For instance, the adjacent formations are typically conductive while the reservoir is not. The present invention provides a method and apparatus for navigating a reservoir using measurements of electromagnetic properties of formations.